The key in parenting is to let them know you understand how they feel and then to teach them how to handle their frustrations. In the case of a child lashing out and saying,"I hate you!" when they are angry, you need to teach them how to act when they are so frustrated. They only know that they are mad, but they have not yet learned self discipline to manage that feeling.
The first thing to realize is that when a child is angry, in that moment you will not be able to teach them anything. Teaching cannot occur until they are in more control. In the case of the child lashing out, I would say," I can see that you are really angry with me but in our family we do not say those things. I want to talk to you but you will have to use your words." If they continue to verbally lash out, then they need to have a short time out until they can get control of their feeling so you can talk to them. You should not tolerate that sort of language in your home as it causes the spirit to leave. We will be discussing this topic in much more detail when we do our classes on discipline. Watch the blog to those notes.